To form a membrane roof system, separate membrane sheets of rubber must generally be overlapped and spliced together to form one continuous water impervious membrane. Membrane sheets can be manufactured up to several hundred feet in length, but are limited to about fifty feet in width. To cover the entire surface area of a roof deck that is more than fifty feet wide, the overlapped membrane sheets must be adhered along numerous water impermeable seams by forming field splices.
A field splice is formed by bonding together overlapping edges of adjacent membrane sheets, i.e., the lower surface of an edge of a first membrane sheet is bonded to the upper surface of an edge of a second membrane sheet. The field splice, which is about three to twelve inches wide, generally includes a thin layer of an internal splicing adhesive or cement which provides a strong secure bond between the two sheets. The field splice also includes a bead of lap sealant either between the overlapped edges of the field splice or at the exposed edge of the splice.
The membrane is held to the roof deck in one of several ways. For example, the roof system can be secured over its entirety with adhesive. Alternately, the roof system can be secured solely with ballast. Another approach employs mechanical fasteners.
Generally, roofing systems of this type last about fifteen years. Because manufacturers often sell roofing systems or various roofing products with a guarantee as to their durability, it is desirable that the manufacturer or dealer have some method for readily identifying the manufacturer of the component roofing parts.
Purdy, U.S. Pat. No. 1,447,265, entitled Means of Identifying Prepared Roofing, discloses the incorporation of a red thread into prepared roofing products in order to provide a permanent means of identification.
Speer, U.S. Pat. No. 1,480,023 entitled Composition Roofing, discloses asphalt roofing material having designs or marks cut into the underside thereof at regularly spaced intervals to provide identifying data such as trademarks or the like.
Although these methods of identifying the origin of manufacture of certain roofing material may be effective in identifying the separate sheets of various roofing systems over a period of time, they have not proved helpful in identifying the origin of the adhesive or lap sealant used along the overlapped seams.
When a failure occurs along a seam, it is imperative to determine the origin of manufacture of the adhesive or lap sealant that was originally used. Substances of this type are generally kept in tubes or containers which are readily identifiable prior to use. However, after application there is no good way of determining from which container the substances were taken, especially years after application.
Chemical analysis of the sealant or adhesive after application requires destruction of the roof. This poses a dilemma for the membrane roofing manufacturer who guarantees a roof system formed of component materials that are installed by an independent contractor. There is no simple way of determining, with any degree of certainty, whose lap sealants or adhesives were used when the roof system was installed.
Identifying articles with ferromagnetic properties has been used for various applications. Pokalsky, U.S. Pat. No. 4,568,921 discloses special responder targets having a high magnetic permeability and being affixed to various items of merchandise so as to be detectable by monitoring the magnetic fields produced by the responder targets on protected articles when the articles are carried through a zone in which an alternating magnetic field is generated.
Kirk U.S. Pat. No. 4,442,152 discloses a marker tape for marking the positions of structural members behind wall panels. The tape is attached to one side of a structural member, such as wall studs, so that the location of the member can be determined after it is covered by a wall, ceiling or floor panel. No such systems has ever been applied to roofing materials or components thereof.